One sore point seems to remain : Apple HomeKit certification apparently not only applies to the Hue bridge but also to the lamps connected to the Hue Bridge :

Before the 1.11 software update, a bug in the Philips Hue system allowed some non-Apple HomeKit certified lights to work with Apple HomeKit. Our 1.11 software update removed the bug with the result that non-Apple HomeKit certified lights no longer work with Apple HomeKit. This remains the case.